Isolation And Mutation Of High Efficiency Phosphorus Solubilizing Penicillium And Exploration On Preparation Of Microbial Fertilizer Using Brewery’s Spent Grains

Phosphorus is one of the essential nutrients for the growth of many plants and also plays an irreplaceable role in soil ecosystems.Soils are rich in phosphorus,but the effective phosphorus content that can be used by plants is low.Chemical phosphorus fertilizers are also increasingly restricted in use due to environmental pollution and ecological damage.Efficient phosphorus solubilizing microorganisms are important to make full utilization of potential phosphorus resources in the soil and alleviate the shortage of phosphorus resources.Moreover,the new phosphorus solubilizing bacterial fertilizer has green and environmental advantages and has been favored in recent years.In this study,a research was conducted among farmers and beer producers about the market prospect of using brewer’s spent grains to prepare phosphorus solubilizing bacterial fertilizer,and the results showed that using brewer’s spent grains to prepare phosphorus solubilizing bacterial fertilizer has a large market value.In this paper,phosphorus-solubilizing fungus YTY with high phosphorus-solubilizing ability was isolated from crop rhizosphere soil,and the fungus YTY was identified as Penicillium oxalicum by morphology and molecular science.and the phosphorus-solubilizing ability,organic acid,p H and so on were explored for P.oxalicum YTY.Then,YTY was irradiated by low-energy ion beam,and the mutant strain P1 with the best phosphate solubilizing effect was obtained by primary sieving in a plate and re-screening in a shaker.The microbial fertilizer fermentation parameters of mutant strain P1,p H,temperature,inoculum and fermentation time,were researched during using brewery’s spent grain.and then the best fermentation parameters were determined by response surface methodology.The main results of this study are as follows.The results of the survey of farmers showed that traditional chemical fertilizers could not meet the immediate needs of farmers,and the 79.16%of farmers were willing to try new fertilizers in the planting process.Due to the decrease in soil fertility caused by the use of chemical fertilizers,65.01%of farmers were willing to change to biofertilizers.In the survey about beer producers,it was found that 65.53%of beer companies agreed to process brewery’s spent grains into microbial fertilizers and thought that using brewer’s spent grains to product biofertilizer might become a more suitable choice.In conclusion,the development and preparation of biofertilizer using brewery’s spent grains raw materials can both improve the economic added value of brewery’s spent grains and provide a new type of green and environmentally friendly microbial fertilizer.This study has far-reaching significance in terms of environmental protection,resource reuse,and sustainable agricultural development.The phosphate solubilizing fungus YTY with high phosphate solubilizing ability was isolated from crop rhizosphere soil,and was identified as Penicillium oxalicum by morphology and ITS sequence analysis.The phosphate solubilizing ability of P.oxalicum YTY was 186.4 mg/L.The YTY secreted three organic acids,acetic acid,lactic acid and oxalic acid during solubilizing Ca₃（PO₄）₂,and by which the YTY lowered the environmental p H to achieve phosphate solubilization.Three positive mutant strains P1,P2 and P3 were selected by low energy ion beam irradiated P.oxalicum YTY,which phosphorus solubilization abilities were291.8,264.6 and 245.8 mg/L,enhanced by 56.88%,42.26%and 32.15%,respectively.Obviously,the mutant strain P1 had the highest phosphorus solubilizing ability.The total organic acids were 0.2072,0.2184 and0.1598 mmol/L for P1,P2 and P3,respectively,were 68.73%,77.85%and 30.13%higher than those of YTY.Consequently,the mutant strain P1 was identified as the optimal strain for the following research because of its strongest ability in the phosphorus solubilization and organic acid secreting.The mutant P1 fermentation conditions of producing phosphate solubilizing microbial fertilizer were explored.And single factor experiment showed that p H 6.5,inoculum level 8%,fermentation temperature 30°C and fermentation time 5d were best.The optimal fermentation conditions of brewery’s spent grain phosphorus solubilizing fertilizer for P1 were obtained by using response surface methodology.The optimal fermentation conditions for P1 were p H 6.804,temperature 28.34°C,inoculum level 10.79%and fermentation time 5.982 d.The study provides technical and theoretical guidance for the development and future industrial production of P.oxalicum P1.